PHP <5.3.4 compat (is_a() usage)

Our build infrastructure still runs an ancient 5.3.3,
and given this is the only blocker for it, worth
complicating the code a bit to retain this compatibility.
removed ref to InheritSideBar
Merge pull request #108 from heffaklump90/master

removed ref to InheritSideBar
Danish translations updated from Transifex
Merge pull request #109 from anselmdk/danish-translations

Danish translations updated from Transifex